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The Journal of North American Herpetology
Volume 2014(1): 87-92
2 July 2014
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EVIDENCE OF COMMUNAL OVIPOSITION AND NEST
ABANDONMENT IN THE NORTHERN TWO-LINED
SALAMANDER (EURYCEA BISLINEATA, (GREEN, 1818)) IN
NORTHEASTERN CONNECTICUT
TAYLOR F. FERGUSON1, ELIZABETH K. TIMPE1, AND ELIZABETH L. JOCKUSCH1*
Department of Ecology & Evolutionary Biology, University of Connecticut, 75 N. Eagleville Rd., U-3043,
Storrs, CT 06269-3043, USA
*
corresponding author contact information: [email protected] (e-mail), 860-486-4452
(phone); 860-486-6364 (FAX)
1
ABSTRACT: Most plethodontid salamanders oviposit their eggs in an individual nest and attend the clutch until hatching. Here, we describe aspects of the reproduction of Eurycea bislineata (Northern Two-lined Salamander) from three
field sites in northeastern Connecticut that contrast with the typical plethodontid reproductive behavior. Rocks used
as oviposition sites contained up to 296 eggs, with an average of more than 100. These numbers exceed the maximum ovarian egg counts for this species, indicating that communal oviposition is common. The lack of correlation
between rock size and number of eggs, as well as the lack of discrete clutches when eggs are laid in large clusters,
suggests that communal oviposition may be caused by something other than nest site limitation. Additionally, the rate
of maternal attendance at nests was low. Thus, communal oviposition with high rates of nest abandonment is the
dominant reproductive strategy in E. bislineata at these sites.
INTRODUCTION
Species that occupy broad geographic ranges provide
an opportunity to study how variation in ecological parameters can cause variation in life history characteristics. Important ecological parameters include photoperiod, temperature, precipitation, resource distribution, and
predator abundance (Morrison and Hero 2003). Reports
of variation in life history are necessary in order to better
understand the factors that drive intra- and interspecific
variation. In amphibians, some life history traits, such
as breeding season and length, are evolutionarily labile
even within species (e.g., Howard and Wallace 1985;
Jockusch and Mahoney 1997), while other traits remain
fixed over long evolutionary periods. Ancestrally, salamanders in the family Plethodontidae were characterized
by a life cycle in which females oviposited their eggs
as a single clutch and then guarded them throughout
embryogenesis (Ryan and Bruce 2000). These life history traits appear to be retained by most extant species
(Crump 1996; Wells 2007). Egg guarding is regarded as
a means of increasing hatching success, with studies of
Desmognathus spp. showing that removal of the brooding female almost always results in complete mortality
of the clutch (Jaeger and Forester 1993). The female’s
presence has been hypothesized to protect eggs from
desiccation, microbial infection, and predation, and to
provide increased aeration to aquatic eggs (Wells 2007).
Absence of maternal care is rare in plethodontids, but
has been noted for several taxa, including multiple species in the bolitoglossine genera Batrachoseps and Nototriton (Jockusch and Mahoney 1997). Solitary oviposition
is also retained by the majority of plethodontid species,
but communal oviposition has evolved multiple times,
including in Hemidactylium scutatum (Four-toed Salamander), Batrachoseps, and Nototriton (Jockusch and
Mahoney 1997).
The Northern Two-lined Salamander (Eurycea bislineata) has previously been described as exhibiting nesting behaviors typical of plethodontid salamanders: female brooding of eggs until hatching and little sharing of
oviposition sites (Bishop 1941; Petranka 1998). Previous
studies documenting the nesting ecology of E. bislineata
have reported relatively small nest sizes, with the mean
number of eggs ranging from 15.4 (Bahret 1996) to 34
(Stewart 1956; Table 1). These are below the reported mean ovarian egg complement of 46 (Stewart 1968).
These reports come from throughout the range of the
species, which extends across northeastern North America, from Labrador and Northern Quebec south to Virginia
and west to Ohio. However, in some reports, the maximum egg count far exceeded the expected clutch size:
121 (Stewart 1956), 165 (Bishop 1941; LeGros 2011),
225 (Weber 1928; Table 1). These findings are suggestive of communal oviposition, although it is clearly not
Journal of North American Herpetology 2014(1)87
the predominant strategy as the finding of large nests almost always occurred in isolation and mean clutch sizes
reported are much lower. Here, the nesting ecology of E.
bislineata is reported from three field sites in northeastern Connecticut. In these populations, communal oviposition is the dominant breeding strategy. In addition, we
report a relatively low proportion of nests with female
attendance.
MATERIALS AND METHODS
Study site
Nests of E. bislineata were observed at three field sites in
Tolland County, Connecticut. Two sites were located on the
University of Connecticut’s Storrs campus (UConn), with
one stream located in the UConn Forest (N 41.82544°, W
72.24985°) and the other in the Hillside Environmental
Education Park (HEEP; N 41.81905°, W 72.26990°). The
third site was located at Gay City State Park in Hebron,
CT (N 41.72595°, W 72.44973°). These sites are separated by 1.8–19.9 km. All sites contained running homogeneous streams or brooks located in mixed deciduous
forests (Figure 1A). Much of the streambed was covered
in rocks, providing numerous possible nesting substrates.
Syntopic species encountered include Desmognathus fuscus (Northern Dusky Salamander), Lithobates clamitans
(Green Frog), L. palustris (Pickerel Frog), dragonfly larvae, and crayfish (Cambarus spp.).
Field sampling
Field work occurred from 25 April - 1 June 2012. Nests
were located by turning over rocks along the streambed
starting at a fixed point (usually where the stream bisected the marked trail) and moving along the stream. We
attempted to examine all rocks except those too large
or deeply embedded in the substrate to lift. Undersides
of rocks were inspected for the presence of eggs. Forty-three nests were found, and 23 nests were collected
for developmental observation in the lab. Two nests were
monitored in the field for the same purpose. Nests were
photographed with a Canon EOS Rebel T3 12.2 MP CMOS
Digital SLR camera. The egg count of each nest was determined in the lab using the count feature in the shareware software package ImageJ (Rasband 2014). For the
25 nests used for developmental observation, the developmental stage of eggs was recorded as were the maximum length and width of the rock. Rock surface area was
estimated as the product of these measurements.
In order to locate attending E. bislineata females, rocks
were lifted carefully so as to minimize the amount of debris and silt clouding the water. In contrast to the behavior of E. bislineata that were not attending clutches,
those found in association with eggs tended to remain
stationary when exposed. If no females were attending
the nest then all rocks and vegetation in the surrounding
area were searched. Nests were treated as attended if a
female was found in the immediate surroundings; this
gives a conservative estimate of the rate of nest abandonment.
Statistical analyses
We used ANOVA to test for differences among sites in
the number of eggs found in a nest. Linear regression
was used to test for relationships between rock size
(surface area or maximum length) and number of eggs.
Sever (2005) advised considering any clutch exceeding
50 eggs as deposited by more than a single female. To
be conservative, we treated any nest exceeding 60 eggs
as communal, while nests with 60 or fewer eggs were
treated as belonging to a single female. We used Fisher
exact tests to evaluate correlations between communal
nesting and female attendance as well as between developmental stage (pre-neurulation vs. later) and female
attendance. All statistical tests were conducted in R v.
2.15.2 (R Development Core Team 2012).
RESULTS
Between 25 April and 1 June 2012, 43 nests were
found. (We define nests as spatially separated clusters
of eggs.) 42 rocks were used as oviposition sites; in one
instance, two spatially separated clusters of eggs were
present on a single rock (Figure 1E). One nest was not
photographed and thus was left out of the analyses because egg count could not be determined. Mean nest size
Figure 1: Field observations of reproduction in E. bislineata. A)
Stream at the Hillside Environmental Education Park (HEEP) field
site showing that the streambed is largely covered in rocks; B)
gravid female from HEEP found under a rock that already contained 53 eggs; C) nest containing 296 eggs, all at similar developmental stages; D) nest containing 263 eggs in two different
developmental stages; E) rock with two discrete clusters of eggs,
containing 55 (left) and 69 (right) eggs.
© The Center for North American Herpetology
Figure 2: A) Distribution of nest sizes (number of eggs) at three
field sites. Black diamonds indicate average for each site. B)
Scatterplot of number of eggs vs. rock surface area. Color indicates site, as shown in the legend. No significant relationship
was detected.
88
Table 1: Nest sizes and fecundity in E. bislineata and its close relatives.
N
range
Nest size meanLocality
E. bislineata
-
30–50
-
Massachusetts
-
12–36
18
Massachusetts
1
225
225
New York
19
3–41
25
Not listed
6
18–43; 68b,c; 165
31
New York
11
6–121
34
New York
-
19–86
46
New York
15
22–53
35.7 New York
11
5–28
15.4 New York
2
35–165
100.0 Ontario, Canada
43
21–296
105.0 Connecticut
E. cirrigera
8
1–34
20
North Carolina
2
42–45
43.5 Virginia
10222–95 50d Ohio
29
18–96; 134c; 180; 257
52.3 Virginia
41
29–115
71.5 Virginia
1
36
36
Georgia
1
36
36
Ohio
7
40–59
52
Alabama/Louisiana
-
15–114
50
Alabama
49
15–110
39.4 Ohio
7
-
53
Mississippi
405
1–117
29.8 Illinois
6
36–59
47.2 West Virginia
37
10–72
36.0 Georgia
9
32–71
55.1 Tennessee (cave)
4
29–79
53.0 Tennessee (surface)
E. wilderae
1
87
87
North Carolina
1
23
23
North Carolina
1
20
20
North Carolina
16
28–56
40.9 North Carolina
3
8–34
21.3 North Carolina
E. aquatica
41
31–138
65.9 Alabama/Georgia
7
60–96
80
-
E. junaluska
4
30–49
37.5 North Carolina
10
41–68
51.0 Tennessee/North Carolina
1
40
40
North Carolina
Source
Wilder 1899
Wilder 1924
Weber 1928
Noble and Richards 1932a
Bishop 1941
Stewart 1956
Stewart 1968
Jockusch (unpublished data)
Bahret 1996
LeGros 2011
this study
Noble and Richards 1932a
Richmond 1945
Wood and Duellman 1951
Wood and McCutcheon 1954
Wood and McCutcheon 1954
Martoff 1955
Siebert and Brandon 1960
Rose and Bush 1963
Mount 1975
Baumann and Huels 1982
Marshall 1996
Jakubanis et al. 2008
Brophy and Pauley 2002
Guy et al. 2004
Niemiller and Miller 2007
Niemiller and Miller 2007
Wood 1949
Bruce 1982
Sever 1983
Bruce 1988
Ryan 1995
Graham et al. 2010
Rose and Bush 1963
Bruce 1982
Sever 1983
Ryan 1998
Shaded rows indicate data from ovarian counts or, in two cases (Jockusch unpublished and Noble and Richards 1932), hormonally
induced oviposition in the lab. Jockusch added enlarged ova that were visible through the body wall after oviposition to her totals.
Noble and Richards noted that most females oviposited completely, and the others retained only a few eggs.
b
Contained eggs at two developmental stages
c
Numbers listed after range were not included in reported mean
d
Median, instead of mean
a
was 105.0 ± 76.1 eggs (range = 21–296) and did not differ significantly across sites (Figure 2A; ANOVA, F=1.80,
d.f.=2, 39, p=0.18; x = 95.5 ± 77.1, n=13 (HEEP); x =
60.0 ± 35.1, n=6 (Gay City); x = 122.2 ± 79.7, n=23
(UConn Forest)). Using the threshold of 60 eggs, 62%
(26 of 42) of nests, containing 85% of eggs (3769 of
4411 eggs), were communal (Fig. 1C-D). Egg counts in
18 nests exceeded the maximum reported ovum count
(86) for E. bislineata (Stewart 1968; Table 1). The mean
egg count for nests treated as solitary was 40.1 ± 9.2;
in three of these, the number of eggs exceeded Sever’s
(2005) recommended cut-off of 50. The mean egg count
for nests treated as communal was 145.0 ± 71.4. In a
few cases, it was clear that eggs in a single nest were
in varying developmental stages (Figure 1D). However,
most large nests contained eggs that were relatively uniform in developmental stage. No relationship was detected between the size of rocks used as oviposition sites
and the number of eggs oviposited on it (Figure 2B; rock
surface area: r2 = 0.049, p=0.30; maximum rock axis:
Journal of North American Herpetology 2014(1)89
r2 = 0.012, p=0.61).
Information on female attendance was collected only
for those nests used for developmental observation
(n=25). Overall, females were found at 11 of 25 nests
(44%). There were three cases in which two females
were found in close association with a single nest (i.e.,
under the same rock). Of the fourteen females found in
association with these nests, three females were very
clearly gravid. However, it is unlikely that gravid females
produced the eggs of the nest they were found with, as
egg counts were over 40 in each nest and the females
were highly gravid (Figure 1B). Attendance excluding the
gravid females was 32% (8 of 25 nests). There was no
association between whether or not a nest was communal and whether or not it was attended (Fisher’s exact
test, p=0.66). Females were significantly more likely to
be present at nests containing embryos in early developmental stages (Fisher’s exact test, p=0.039). Four of six
nests in which embryos had not yet reached neurulation
were attended, while only three of 18 later-stage nests
were. (One nest was excluded from these analyses because egg count and stage were not recorded.)
DISCUSSION
Evidence for communal oviposition
Field data collected from northeastern Connecticut indicate that E. bislineata in this region exhibited a communal nesting strategy with surprisingly low frequency
of female nest attendance. Based on Sever’s (2005) indication that nests with more than 50 eggs are likely the
product of more than one female, communal nests were
present in all three field sites. The mean and maximum
egg counts found in this study were much higher than
previously reported numbers for other populations of this
species (Table 1). Our maximum egg counts are particularly compelling; for example, nest sizes of 263, 291, and
296 greatly exceed the largest ovarian egg count (Table
1) and are most certainly the work of multiple females,
possibly five or more. Similarity of developmental stage
within a communal nest indicates that all eggs were usually oviposited within a short time frame.
Communal oviposition has been observed in only about
7% of species within the family Plethodontidae (Doody et
al. 2009). Communal nesting has also been recorded in a
close relative of E. bislineata, E. cirrigera (Southern Twolined Salamander), in Illinois, where 8% of nests had egg
counts exceeding the maximum ovarian egg count for
this species (Jakubanis et al. 2008). Other plethodontid
genera that regularly exhibit communal nesting include
Hemidactylium, Nototriton, and Batrachoseps (Jockusch and Mahoney 1997). Nototriton and Batrachoseps
are both direct developers that oviposit terrestrially. Although H. scutatum retains the ancestral biphasic life cycle, it also oviposits terrestrially. It is the only plethodontid species in which communal nesting has been studied.
It is known to exhibit both solitary and joint nesting in a
single population, with the latter comprising 19–52% of
all nests (Harris and Gill 1980; Harris et al. 1995).
Many hypotheses have been proposed to explain the
evolution of communal nesting. These can generally be
divided into two categories. One category posits adaptive
explanations and the other posits a “by-product” mechanism wherein the behavior is a secondary outcome of
some other coincidental factor causing the aggregation
of nesting females (Doody et al. 2009). Hypothesized
causes of communal nesting include saturated habitat,
aggressive usurpation, intraspecific brood parasitism,
multiple defenders, predation dilution, and kin selection
© The Center for North American Herpetology
(summarized in Harris et al. 1995). There is a growing
body of evidence supporting adaptive explanations over
‘by-product’ hypotheses, such as saturated habitat, in diverse taxa (Doody et al. 2009).
Before considering adaptive explanations for communal
oviposition, the by-product hypothesis of habitat saturation should be considered (Doody et al. 2009). In an
experimental setting, females in both high and low density populations chose to oviposit communally at similar
frequencies, thus refuting habitat saturation as a viable
explanation in H. scutatum (Harris et al. 1995). By contrast, oviposition site limitation has been suggested for
several populations of E. cirrigera. Baumann and Huels
(1982) found a positive correlation between number of
eggs and rock size, as a result of multiple, separated
nests occurring more frequently on larger rocks. Similarly, in an Illinois population of E. cirrigera, rocks with
a larger maximum dimension were more likely to have
multiple, spatially separated nests (Jakubanis et al.
2008), although no correlation between number of eggs
and rock surface area was found. Finally, artificial substrates were used for oviposition in one of two Georgia
populations in which they were provided, also suggesting that oviposition substrates were limited (Guy et al.
2004).
It does not appear that there is oviposition site-limitation in our study population of E. bislineata. One prediction of the habitat saturation hypothesis is that larger
rocks will have more eggs. This prediction was not supported using either surface area or maximum length as
the measure of size. Additionally, even when the eggs
on a large rock were oviposited by multiple females,
they tended to be tightly clustered rather than placed
in discrete clutches, as is often observed when E. cirrigera share an oviposition substrate (Baumann and Huels
1982). Another piece of evidence against the habitat saturation hypothesis is that eggs on a single rock appeared
to be more similar in stage than eggs in the entire population. However, further work is needed to test this pattern. If habitat saturation were the cause of communal
oviposition, then clutches oviposited together would be
predicted to be more divergent in stage. Finally, although
we did not quantify the proportion of rocks used for oviposition, only a small proportion of the available rocks
were used, and many unused rocks appeared similar to
those used for oviposition. Thus, our data point toward
an adaptive explanation for communal oviposition in E.
bislineata in northeastern Connecticut. Nonetheless, it is
difficult to completely rule out the habitat saturation hypothesis. It might be difficult to quantify which aspects
of a nest site make it of higher quality than others for
an organism. Though nest sites may seem in apparent
abundance, those of the highest quality might actually
be saturated.
Female nest attendance
For plethodontid salamanders, maternal attendance
is usually the rule, with few exceptions (Jockusch and
Mahoney 1997). Our data indicate that female parental
care in the form of brooding behavior is largely absent in
our study populations of E. bislineata. We found that a
high proportion of nests were unattended, with attending females present at only 17% of nests in which eggs
had reached neurulation (compared to 67% of nests in
which eggs were at an earlier developmental stage). This
suggests that the typical pattern is for a female to remain with her clutch briefly before abandoning it. This
underlines that there are costs associated with parental
90
care behavior. Providing care to eggs may be energetically expensive, reduce investment in future offspring,
and incur physical risk to the parent if engaging in defensive behavior (Wells 2007). An experimental study in
Plethodon cinereus (Red-backed Salamander) found that
females who engaged in brooding behavior produced
smaller eggs in subsequent seasons than those who did
not brood (Yurewicz and Wilbur 2004).
Joint nests in H. scutatum usually have only one brooder, suggesting the abandonment of at least one other
female (Harris et al. 1995). Nest abandonment in our
study populations of E. bislineata may represent another
step in the continuum where all females of a communal
nest abandon, perhaps because the costs of attendance
outweigh the benefits due to the predator dilution effect.
Further, a few of the nests that were obviously communal
in E. bislineata did have a single female brooder. Additional study is needed to determine if a single female
at a communal nest represents the first or last ovipositor, which would provide more insight into the reason for
abandonment by one or multiple females.
In both E. bislineata and H. scutatum, communal oviposition either precedes or originates concomitantly
with nest abandonment. By contrast, Jockusch and Mahoney (1997) found that loss of female attendance likely
preceded the evolution of communal nesting in Batrachoseps and Nototriton, suggesting that there are multiple evolutionary paths to the evolution of unattended
communal nests in plethodontids. The frequent co-occurrence of these two rare traits, combined with evidence
for multiple routes to the same outcome, suggests that
communal oviposition may lower the benefits of providing maternal care, while nest abandonment may increase
the benefit of communal oviposition.
There is a trend for longer embryonic periods in salamanders that live in flowing aquatic environments compared to other aquatic habitats; this naturally increases
the predation risk on clutches. Nussbaum (1985) proposed that longer embryonic period selected not only for
hidden nest sites but also for the evolution of maternal
attendance in stream-dwelling species. This is exemplified by his summary of parental care in aquatic-nesting
salamanders: only three lentic-nesters exhibit parental
care, and the behavior is largely confined to lotic-nesters
in the family Plethodontidae, with E. bislineata included
(Nussbaum 1985). It seems that a lack of parental care
in this species has only previously been reported in the
literature when the substrate or habitat of egg deposition
was unusual. Wood (1953) found an egg mass attached
to a pile of dead leaves with no female present, though
this may be attributed to the dimensional complexity
of the oviposition site, allowing females to escape detection. Bahret (1996) found nests of E. bislineata in a
lake at a mean depth of 11.3 m, also without attendant
females. It should be noted that besides these unusual
cases, most natural history reports of E. bislineata lack
data on female nest attendance. One explanation for
this lack is that it is widely accepted that E. bislineata
females provide parental care (Bishop 1941; Petranka
1998) and thus it becomes unnecessary to report. Alternatively, it may be that females are often not observed,
but this has not been reported, perhaps because of uncertainty about whether a female fled. Without additional
data on the presence or absence of females at nests, it
remains largely unknown whether E. bislineata exhibits
consistent maternal care behavior throughout most of
its range. In E. cirrigera, female attendance is generally reported (e.g., Richmond 1945; Baumann and Huels
1982; Marshall 1996; Pauley and Watson 2005), but one
study found low rates ranging from 0–50% depending on
year and study population (Jakubanis et al. 2008). Other areas where low rates of nest attendance have been
reported for E. cirrigera are West Virginia (Brophy and
Pauley 2002) and cave sites in Tennessee (Niemiller and
Miller 2007).
Geographic variation in reproductive biology
Because E. bislineata is a species that occupies a broad
geographic range, it offers the opportunity to study how
changing ecological parameters affect important life history traits. Our study documented the nesting ecology
of E. bislineata in northeastern Connecticut and has provided preliminary evidence of variation in nesting strategy and parental care behavior in this species. Though
communal oviposition in E. bislineata is not a novel observation (Table 1), the predominance of joint nesting
in a single population has not been observed elsewhere.
It is possible that some ecological factor in our study
region selects for communal oviposition. Further, either
the same or different factors, including communal oviposition itself, may be largely responsible for female abandonment of eggs at some point during the embryonic
period. These factors may include increased predation
levels, resource distribution, competition with syntopic
species, changes in population density, changes in embryonic development period, or some combination of
these factors. Additional study is needed to determine
what factors have led to communal oviposition and nest
abandonment by E. bislineata in northeastern Connecticut and the degree to which this life history strategy is
found in other regions.
ACKNOWLEDGMENTS
We would like to thank the University of Connecticut Office of Undergraduate Research for funding this research
project through a Summer Undergraduate Research
Fund award to TFF, as well as members of the Jockusch
lab for support and advice during the execution of this
research. Organisms were handled and collected under
CT Scientific Collecting Permit #0913008 to ELJ.
LITERATURE CITED
Bahret, R. 1996. Ecology of lake dwelling Eurycea bislineata in the Shawangunk Mountains, New York. Journal of Herpetology 30:399–401.
Baumann, W. L., and M. Huels. 1982. Nests of the Twolined Salamander, Eurycea bislineata. Journal of Herpetology 16:81–83.
Bishop, S. C. 1941. Salamanders of New York. New York
State Museum Bulletin 324:1–365.
Brophy, T. R., and T. K. Pauley. 2002. Reproduction in
West Virginia populations of the Southern Two-lined
Salamander (Eurycea cirrigera). The Maryland Naturalist 45:13–22.
Bruce, R. C. 1982. Egg-laying, larval periods and metamorphosis of Eurycea bislineata and E. junaluska at
Santeetlah Creek, North Carolina. Copeia 4:755–762.
Bruce, R. C. 1988. An ecological life table for the salamander Eurycea wilderae. Copeia 1988:15–26.
Crump, M. L. 1996. Parental care among the Amphibia.
Pp. 109–144 in Rosenblatt, J. T., and C. T. Snowdon
(eds.), Parental Care: Evolution, Mechanisms, and
Adaptive Significance, Advances in the Study of Behavior, v. 25. Academic Press, San Diego.
Doody, J. S., S. Freedberg, and J. S. Keogh. 2009: Communal egg-laying in reptiles and amphibians: evolu-
Journal of North American Herpetology 2014(1)91
tionary patterns and hypotheses. Quarterly Review
of Biology 84:229–252.
Graham, S. P., E. K. Timpe, M. Alcorn, and J. Deitloff.
2010. Notes on the reproduction in the brownback
salamander (Eurycea aquatica). IRCF Reptiles & Amphibians 17:168–172.
Guy, C. J., R. E. Ratajczak Jr., and G. D. Grossman. 2004.
Nest-site selection by Southern Two-lined Salamanders (Eurycea cirrigera) in the Georgia Piedmont.
Southeastern Naturalist 3:75–88.
Harris, R. N., and D. E. Gill. 1980. Communal nesting,
brooding behavior, and embryonic survival of the
four-toed salamander, Hemidactylium scutatum.
Herpetologica 36:141–144.
Harris, R. N., W. W. Hames, I. T. Knight, C. A. Carreno, and T. J. Vess. 1995. An experimental analysis of
joint nesting in the salamander Hemidactylium scutatum (Caudata: Plethodontidae): the effects of population density. Animal Behaviour 50:1309–1316.
Howard, J. H., and R. L. Wallace. 1985. Life history characteristics of populations of the long-toed salamander (Ambystoma macrodactylum) from different altitudes. American Midland Naturalist 113:361–372.
Jaeger, R. B., and D. C. Forester. 1993. Social behavior
of plethodontid salamanders. Herpetologica 49:163–
175.
Jakubanis, J., M. J. Dreslik, and C. A. Phillips. 2008. Nest
ecology of Southern Two-lined Salamander (Eurycea
cirrigera) in eastern Illinois. Northeastern Naturalist
15:131–140.
Jockusch, E. L., and M. J. Mahoney. 1997. Communal oviposition and lack of parental care in Batrachoseps nigriventris with a discussion of the evolution of breeding behavior in plethodontid salamanders. Copeia
1997:697–705.
LeGros, D. L. 2011. Communal oviposition in the Northern Two-lined Salamander (Eurycea bislineata) in Algonquin Provincial Park, Ontario. Canadian Field-Naturalist 125:363–365.
Marshall, J. L. 1996. Eurycea cirrigera (Southern Twolined Salamander) nest site. Herpetological Review
27:75–76.
Martoff, B. 1955. Observations on the life history and
ecology of the amphibians of the Athens area, Georgia. Copeia 1955:166–170.
Morrison, C., and J. Hero. 2003. Geographic variation in
life-history characteristics of amphibians: a review.
Journal of Animal Ecology 72:270–279.
Mount, R. H. 1975. The Reptiles and Amphibians of Alabama. University of Alabama Press, Tuscaloosa, AL.
Niemiller, M. L., and B. T. Miller. 2007. Subterranean reproduction of the Southern Two-lined Salamander
(Eurycea cirrigera) from Short Mountain, Tennessee.
Herpetological Conservation and Biology 2:106–112.
Noble, G. K. and L. B. Richards. 1932. Experiments on
the egg-laying of salamanders. American Museum
Novitates 513:1–25.
Nussbaum, R. A. 1985. The evolution of parental care in
salamanders. Miscellaneous Publications, Museum of
Zoology, University of Michigan 169:1–50.
Pauley, T. K., and M. B. Watson. 2005. Eurycea cirrigera. Pp. 740–743 in M. Lannoo (ed.), Amphibian Declines: Status of United States Species. University of
California Press, Berkeley.
Petranka, J. W. 1998. Salamanders of the United States
and Canada. Smithsonian Institution Press, Washington, DC.
R Development Core Team. 2012. R: A language and
© The Center for North American Herpetology
environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. ISBN
3-900051-07-0, URL http://www.R-project.org/.
Rasband, W.S. 2014. ImageJ. U. S. National Institutes
of Health, Bethesda, Maryland, USA, http://imagej.
nih.gov/ij/.
Richmond, N. D. 1945. Nesting of the Two-lined Salamander on the Coastal Plain. Copeia 1945:170.
Rose, F. L., and F. M. Bush. 1963. A new species of Eurycea (Amphibia: Caudata) from the southeastern United States. Tulane Studies in Zoology 10:121–128.
Ryan, T. J. 1995. The distribution, larval morphology and
life history of Eurycea junaluska (Amphibia: Caudata: Plethodontidae). M.S. Thesis, Western Carolina
University.
Ryan, T. J. 1998. Larval life history and abundance of a
rare salamander, Eurycea junaluska. Journal of Herpetology 32:10–17.
Ryan, T. J., and R. C. Bruce. 2000. Life history evolution
and adaptive radiation of hemidactyliine salamanders. Pp. 303–326 in Bruce, R.C., R.G. Jaeger and
L.D. Houck (eds.), The Biology of Plethodontid Salamanders. Kluwer Academic/Plenum Publishers, New
York.
Sever, D.M. 1983. Observations on the distribution and
reproduction of the salamander Eurycea junaluska in
Tennessee. Journal of the Tennessee Academy of
Science 58:48–50.
Sever, D. M. 2005. Eurycea bislineata. Pp. 735–738 in
M. Lannoo (ed.), Amphibian Declines the Conservation Status of the United States Species. University of
California Press, Berkeley.
Siebert, D. H., and R. A. Brandon. 1960. The salamanders of southeastern Ohio. Ohio Journal of Science
60:291–303.
Stewart, M. M. 1956. Certain aspects of the natural history and development of the Northern Two-lined Salamander, Eurycea bislineata bislineata (Green), in the
Ithaca, New York, region. Ph. D. Dissertation, Cornell
University.
Stewart, M. M. 1968. Population dynamics of Eurycea
bislineata in New York. Journal of Herpetology 2:
176–177.
Weber, J. A. 1928. Herpetological observations in the Adirondack Mountains, New York. Copeia 169:106–112.
Wells, K. D. 2007. The Ecology and Behavior of Amphibians. University of Chicago Press: Chicago, Illinois.
Wilder, H. H. 1899. Desmognathus fuscus and Spelerpes
bilineatus (Green). American Naturalist 33:231–246.
Wilder, I. W. 1924. The developmental history of Eurycea
bislineata in western Mass. Copeia 133:77–80.
Wood, J. T. 1949. Eurycea bislineata wilderae Dunn. Herpetologica 5:61–62.
Wood, J. T. 1953. The nesting of the Two-lined Salamander, Eurycea bislineata, on the Virginia Coastal Plain.
Natural History Miscellanea No. 122, Chicago Academy of Sciences, Chicago, Illinois.
Wood, J. T., and W. E. Duellman. 1951. Ovarian egg complements in the salamander Eurycea bislineata rivicola Mittleman. Copeia 1951:181.
Wood, J. T., and H. N. McCutcheon. 1954. Ovarian egg
complements and nests of the Two-lined Salamander, Eurycea b. bislineata x cirrigera, from southeastern Virginia. American Midland Naturalist 52:433–
436.
Yurewicz, K. L., and H. M. Wilbur. 2004. Resource availability and costs of reproduction in the salamander
Plethodon cinereus. Copeia 2004:28–36.
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